
\(L_{\text{\,acc}}\)  and \(\dot{M}_{\text{\,acc}}\)  were observed to vary by up to a factor of \(\sim \!2\)  over the 15 nights. This variability is an intrinsic variation of the accretion rates. In particular, it does not reflect variations related to the stellar rotation.

The average value of the mass accretion rate found is \(\dot{M}_{\text{\,acc,\,avg}}={4.8e-8}\,M_{\odot }\,\) yr\(^{-1}\) . This is within the spread of values found in [1]} (\({1.8e-8}\,M_{\odot }\,\) yr\(^{-1}\) ) and [2]} (\({6.7e-8}\,M_{\odot }\,\) yr\(^{-1}\) ).

The wind-tracing emission lines ( [Oi] 6300 Å  and [Sii] 6730 Å) are very stable over the time interval of these observations. They do not reflect the short-term changes in the mass accretion rate.

In comparing the models of [3]}, [4]}, and [5]}, we establish RU Lup is likely to be in an unstable accretion regime.

The Lii 6707 Å  absorption line is measured to have an average EW\(_{{Li}{i}}= 0.17\pm 0.03\)  Å  and an average \(r_{\,{Li}{i}}= 3.25\pm \,0.20\)  when the Li depletion in the template star TAP 45 is taken into account.

The temporal variability pattern over the 15 nights for \(r_{\,{Li}{i}}\)  is strongly correlated to that of \(L_{\text{\,acc}}\)  (see Fig. REF ).

The veiling measured in the photospheric absorption lines Nai 5688 Å  (\(r_{\,{Na}{i},\,\text{avg}}= 3.27\pm 0.63\) ) and Mni 6021 Å  (\(r_{\,{Mn}{i},\,\text{avg}}= 3.29\pm 0.67\) ) demonstrate positive, although different, correlations with the veiling measured in Lii 6707 Å  and \(r_{\,{Li}{i},\,\text{avg}}= 3.25\pm 0.20\) . This reveals the relative importance of emission line veiling in each individual line's total veiling. The veiling found in Mni 6021 Å, for example, increases more rapidly than the other metal lines, given an increase in accretion.

The correlation we detect between changes in the accretion luminosity and changes in the veiling is strong and provides further evidence that the variability observed is not caused by extinction (the veiling measurements are unaffected by extinction because they are obtained by comparing two normalised spectra).

